I went to the Zoological Record database* (see disclaimer at bottom for search parameters) and looked at the classification of different "kinds" of research by echinoderm taxon.
I make no interpretations other than what seems apparent.
Here's what you get:
*Fossil publications recover the greatest number of hits for the Echinodermata, followed by development (thanks Strongylocentrotus!) and then systematics.
*Sea Urchin papers account for about 42% of the TOTAL number of echinoderm publications!! But of, those the majority of sea urchin publications are in development (so...mostly Strongylocentrotus).. None of the other remaining echinoderm groups really reaches this overall percentage of the total.
Asteroids make up about 18% of the total number of publications, breaking down with less. I'll be honest though, its entirely possible that crinoids (14%) are under represented in the ZR database. Crinoids occupy a prominent role in Geology as index fossils which may not be reflected in a zoological context.
Echinodermata (total=39,989 publications)
Fossils 7839 (note that x-ref with Paleontology only got 527 hits)
Class by Class Breakdown... (sorry-Living groups only...didn't get to do Paleozoic groups for now...)
Echinoidea (total=16,888 publications)
Asteroidea (total=7,220 publications)
Crinoidea (total=5,494 publications)
Holothuroidea (total=4,100 publications)
Ophiuroidea (total=3,317 publications)
*Their database extends back to 1864..but I think our access only extends to 1945. In any case, it doesn't make a significant difference-still a LOT of publications. Bear in mind..what you have is probably imperfect, biased and NOT at all as well-thought out as it probably ought to be, so any mistakes or logical errors are mine. (but if I worked all that stuff out-I would probably be submitting this for publication somewhere instead of doing this!)